Receiver and action assembly for firearms



Sept. 3, 1952 vT. RQ ROBINSON, JR 4 RECEIVER AND ACTION- ASSEMBLY FORFIREARMS Filed NOV. 28, i947 Patented Sept. 23, 1952 f .anonrvrnhnnisorron assmviatrron:

, FIREARMS Thomaslt; Robinson, 512, Newton, (Donn, assignor toThe'Marlin Firearms, Company, New Haven;

001111., a corporation of Connecticut Application November 28, 1947,Serial No. 788,530

Y 12 Claims. 1 1

The present invention relates in general to firearms and more especiallyto therecelver, breechboltand trigger plate assembly offan automaticself-loading" firearm.

An; objectvof the rinvention'is to provide an improved. receiver-andbreechsbolt assembly for insuringztreliable and .iuniformi operation' ofa firearm;.

,A'furtherrobjectiof the invention :is to provide improved. breech-bolt.guideemeans in the receiver of.ia.firearm.;whereby the reliable anduniform operation 02 theebreech-obolt :is assured, irrespectiveiofitheaccumulation ofiadventitious material within the'receiver; x

A still furtherzobiect of the: invention'is to pro- ,Vider the:receiver? of 1 a1 firearm with improved breechebolt guide meanssfor:reducing frictional drag; between? the: breech-bolt and the interiorwall of thesreceiver. andifor insuring auniform cycle-of operations;

A" still: further objectofthe invention is to provide the. receiver ofa1 firearm withimproved breech-bolt guide-vmeansswhich is of simple andeconomicalconstruction an'dwhichis adapted to provide means forattaching atrigger-plate to the-underside of the receiver;

With the'above and other object in'view, as-will appear-to those-skilledin the art from the present disclosure, this inventionincludes allfeatures in the said disclosurewhich are novel over the prior art andwhich are notclaimed insany separate application- In the accompanyingdrawings, in which certain modes of carrying out the present inventionare shown for illustrative purposes:

Fig, 1 is-a=sidee1evation of the receiver of an automatic: self-loadingfirearm including a trigger-platetmountedon the underside thereof and afragmentary portion-0f the barrel;

Eigez lissasidewelevationin section of the receiver of 1, on. a.vertical plane through the longitudinal axis thereof:

Fig; 3'is anendelevation. in section on. line .3-3 offFig': 1;,

Fig; 4- isaperspectiVevie'w ofltheireceiver of,

the-=flrearm'shown' in Fig. 1; and

Fig. 5 is aperspective view of the trigger-plate which is secured to theunderside of the receiver, as: shownin Fig: l.

' Referring to the drawingswhich, for the pur- 2 2,454,885, and Ser. No.786,232, filed November 15, 1947, patented December 28, l949',a,s;Patent No. 2,492,814, andcomprising, in the main, areceiverindicatedgenerally at [5, abarrel it f xedly secured to the forward: end thereofand areceiver-elementsuchas, forexample; a triggerplate ll attached tothe underside ofthe receiver.

The latter comprises a substantiallyscylindrical member preferablyformed from a suitable length of tubular steel stock (see Fig: 4),the'rear end of which is closed by'a'receiver-plug 18. The barrel It isadapted to be secured in the forward restricted end ofthe receiver,therestriction of which is provided, for example, by.azrelativelythick-walled bushing I9 welded .or otherwise secured thereinso as to divideth'e interior 'of'the receiver into a forward chamber200i reduced diameter and a concentric axially-aligned rearward chamber2|. The latter ischereinafter referred to as the breech-boltguide-chamber, the inside diameter of which; corresponds substantiallyto theinside diameter of the receiver-tube. Although a receiver"comprising a tubular-member having a cylindrical bushing inserted in oneend thereof to form a composite breech-bolt chamber of two diameters isa highly satisfactory. and economical construction, it'will beappreciated that it is within'the purview of-the invention .to form thereceiver, including the forward 1 and rearward chambers 28 and Elrespectively, from a single piece of stock in any well known andapprovedmanner.

Formed in the underside or bottom. of the breech-bolt guide-chamber 2|of the receiverare a plurality of apertures, indicated-generally at '22,which communicate with thetrigger-plate IT in which the fire-controlmechanism (not shown) is adapted to be mounted. A suitable ejectionport23 is provided intheright-hand side ofthe receiver and comprises asubstantially-longitudinal slot communicating with ..the,forwardiohamrber 20 of the receiver.

Mounted toreciprocate longitudinally inn-the composite breech-boltchamber of thereceiver, is a'breech-bolt, indicated generally at 24;which as shown in-Figs. l and 2 comprisesla substantially-cylindricalrear end-portion 25 'adaptedto be slidably supported: in" thebreech-bolt guidechamber 2! of the. receiver by suitable guidemeans, ashereinafter described; .anda substantially-cylindrical front end-portion26 of reduced diameter adapted to make'a smooth sliding; fit in theforward chamberZU of the receiver. The breech-bolt may be formed .fromtwo .separate cylindrical elements of different external diameters, theelement of smaller external diameter being secured by a welded joint orsimilar fastening-means in the forward end of the element of largerdiameter and in axial alignment therewith. Although a two-piece bolt isquite successful both from the standpoint of operation and economy ofmanufacture, it will be appreciated that the breech-bolt may be turnedout of a single piece of stock. The breech-bolt is adapted to beoperated manually by means of a handle 21 which is detachably securedthereto and projects through the ejection-port 23 of the receiver, thehandle being cooperatively associated therewith to prevent rotation ofthe bolt in the chamber, as more fully described in the applicationsabove identifled. Other details of the breech-bolt such as, for example,its firing-pin (not shown), as well as details of the action mechanism,including the firing-plunger and sear, are the subject-matter of theaforementioned applications and, hence, the present description is notburdened with a description of these elements.

Referring particularly to Figs. 2 and 3, the

' breech-bolt and more especially the enlarged rear end-portion 25thereof is adapted to be supported and guided in the breech-boltguidechamber 2! of the receiver by improved guidemeans comprising ribs28 which extend longitudinally of the breech-bolt guide-chamber and arespaced circumferentially around the inner wall thereof. In thisconnection, it will be noted more especially from Fig. 3 that thediameter of the enlarged rear end-portion 25 of the breech-bolt isappreciably less than the inside diameter of the breech-boltguide-chamber 2|, as a consequence of which the guide-ribs 28 constitutethe sole supporting-means for the rear end-portion of the breech-bolt.In the particular embodiment of the invention illustrated in thedrawings, three such guide-ribs are shown, one rib being at the top ofthe chamber in a vertical plane through the longitudinal axis thereofwhile the two remaining guide-ribs are formed on opposite sidesrespectively of the chamber and at angles of substantially 120 withrespect to the top guide-rib and to each other. Each guide-rib isprovided with alongitudinal bearing surface 29 which is elevated abovethe circumferential plane of the inner wall of the guide-chamber andwhich comprises a concave substantially-cylindrical surface ofrevolution, the radius of which corresponds substantially to the radiusof the enlarged rear end-portion 25 of the breech-bolt. In theembodiment of the invention shown herein, the total area of the bearingsurfaces 29 of the guideribs is as little as twelve-and-one-half percent of the circumferential area of the breech-bolt guide-chamber, as aconsequence of which the breech-bolt reciprocates longitudinally in thechamber with a minimum frictional drag. Moreover, since the breech-boltis supported in spaced relationship to the interior wall. of thebreechbolt chamber, any likelihood of the breech-bolt being fouled bythe accumulation of adventitious material in the receiver, iseffectively obviated. Although the specified ratio of the total area ofthe bearing surfaces of the guide-ribs to the circumferential area ofthe chamber has been found highly satisfactory, it will be understoodthat this ratio is by way of example-only and that it is within thepurview of the invention both to increase or decrease the area of thebearing surfaces within limits consistent with the satisfactoryoperation of the firearm.

The circumferentially spaced guide-ribs 28 of the breech-boltguide-chamber may comprise narrow substantially-solid bars or strips ofmetal spot welded or otherwise secured on the inner wall of the chamber,but as shown especially well in Fig. 3, it is preferred, from thestandpoint of economy, to formthe ribs by a striking-in operationperformed upon the exterior wall of the receiver longitudinally thereofand at circumferentially-spaced points on its perimeter. In this manner,the guide-ribs 28 are formed as integral in-struck portions of thereceiver, the bearing surfaces 29 of which may be formed, for example,by passing a reamer or similar tool lightly along the inner convex edgesthereof to form concave cylindrical surfaces of revolution.Simultaneously, the exterior wall of the receiver opposite thelongitudinal in-struck guide-ribs is formed with longitudinal grooves30. As shown especially well in Fig. 2, the forward ends of theguide-ribs 23 constitute abutments against which the rear end of thebushing I9 is seated in assembling the latter in the receiver.

The longitudinal exterior grooves 30 in opposite sides respectively ofthe receiver constitute means for attaching the trigger-plate I! to theunderside thereof. Referring more especially to Fig. 5, thetrigger-plate comprises a substantially-U-shaped member having spacedparallelsubstantially-vertical sides 3|, each of which is provided atitsupper edge with an outwardly-turned flange 32, the inner face 33 ofwhich, as shown particularly well in Fig. 3, constitutes a concavesubstantially-cylindrical surface of revolution adapted to conform tothe curvature of the exterior wall of the receiver. Moreover, eachflange is provided along its upper edge with an upwardly-projectingin-turned lip 34 which extends longitudinally thereof from the forwardend of the trigger-plate rearwardly for substantially twothirds of itslength, each lip 34 being adapted to engage in one of the correspondinggrooves 30 in the opposite sides of the receiver, the inherentflexibility of the side walls 3| of the trigger-plate serving to holdthe lips 34 thereof resiliently in the corresponding grooves of thereceiver. To further insure that the trigger-plate is attached to thereceiver securely and against longitudinal movement with respectthereto, the concave flange-portions 32 of the trigger-plate may befastened by spot welds 35 or equivalent fasteningmeans to the adjacentwall of the receiver.

By providing longitudinal circumferentiallyspaced guide-ribs 28 on theinner wall of the breech-bolt chamber, relatively-large circumferentialclearance-spaces are maintained between the periphery of the rearend-portion 25 of the breech-bolt and the inner wall of theguidechamber, as a consequence of which the longitudinal reciprocatingmovement of the breechbolt whether by recoil, spring or handmanipulation will be substantially free irrespective of the inclusion ofadventitious material in the breechbolt chamber. It will be evident toothat since the guide-means engages the periphery of the breech-bolt onlyalong longitudinal circumferentially-spaced areas thereof, the resultingcircumferential clearance-spaces between the periphery of thebreech-bolt and the inner wall of'the chamber extend without materialobstruction from front to back of the breech-bolt, thus precluding theformation of an air-cushion between the rear end of the breech-bolt andthe forward end of the receiver-plug. Moreover, by providing guide-ribshaving bearing surfaces of relativelyaeiigeoc small-area; the1r1ctional-dragbnthebreech-bQlt is reducedtoaminimumvalue; I V

- As-a' consequence of these characteristicfeatures of the invention;the operation of the breech-bolt particularly in automatic self-loading'firearms is-reliableand'uniform. In this connection; it shouldbe pointed out that the adaptationof' the invention to anautomaticfirearm is particularly desirable in order to eliminate variations inits-"operationacycle, but that the invention is equally adapted fon usesuccessfully with all firearmshaving;a reciprocablelongitudinallysliding breech b'olt;

The invention-may be carried out in otherspecific ways thanthose hereinset I forthwithout departingfrom the spirit and essentialcharacteristics of theinvention; and; the present embodiments are;therefore; to be considered in all respects as illustrativeand notrestrictive, and all changes coming within the meaning and equivalencyrange-of the appended claims are intended to be embraced therein.

I claim:

1. In a firearm the combination including: a receiver having abreech-bolt chamber; breechb'olt guide-means on the innerrwall thereofsaid gu'ideem'ean's comprisin circumferentially spaced parallel ribsextending longitudinally. of said chamber; and a breech-bolt supportedjnsaid chamber by said ribs in relatively widely-spaced relationship tothe inner wall of said chamber for longitudinal reciprocablemovement insaid chamber.

2: In a firearm the-combination including: a receiver having abreech-bolt chamber; breechbolt guide-means on the inner Wall thereofsaid guide-means comprising circumferentially-spaced parallel ribsextending longitudinally of said chamber, and bearing-surfaces extendinglongitudinally of said ribs, said bearing-surfaces being concentric withrespect to the longitudinal axis of said receiver; and a breech-boltsupported in said chamber on said bearing surfaces for longitudinalreciprocable movement in said chamber.

3. In a firearm the combination including: a receiver having abreech-bolt chamber; breechbolt guide-means on the inner wall thereofsaid guide-means comprising circumferentially-spaced parallel ribsextending longitudinally of said chamber, and bearing-surfaces ofsubstantiallyequal area extending longitudinally of said ribs saidbearing-surfaces being concentric With respect to the longitudinal axisof the said receiver and constituting in area substantially as little astwelve-and-a-half per cent of the corresponding inner circumferentialarea of said chamber; and a breech-bolt supported in said chamber onsaid bearing-surfaces for longitudinal reciprocable.

movement in said chamber.

4. In a firearm the combination including: a receiver having abreech-bolt chamber; breech-= bolt guide-means on the inner wall thereofsaid guide-means comprising cireumferentially-spaced parallel ribsconsisting of metal struck inwardly from the exterior wall of saidchamber and extending longitudinally thereof; and a breech-boltsupported in said chamber on said inwardlystruck ribs in relativelywidely-spaced relationship to the inner wall thereof for longitudinalreciprocable movement in said chamber.

5. In a firearm the combination including: a receiver having abreech-bolt chamber; breechbolt guide-means on the inner wall thereofsaid guide-means comprising circumferentiall -spaced parallel ribsconsisting: of-metalstru'ck inwardly fromtheaexterior'wall oiisaidchamber andextending longitudinally: thereof" and bearing-surfacesextending-longitudinally.of said inwardly struck ribs; said. bearingsurfacescomprising concentric"cplindricalf sufaces of revolution ofsubstantially-equal area and radius; the radius of each concentricsurface being: measured from the longitudinal axis of the receiver; anda breech-bolt supportedin said chamber on the said-bearing surfaces ofsaidinwardly-struck ribs for-longitudinal reciprocable movement in saidchamber.

6; In a firearm-the combination including: a receiver havingabreech-bolt chamber; breechbolt guide means on the inner wall ofsaidchamber comprising longitudinal circumferentiallydiscontinuousbearing-surfaces struck inwardly from-the exterior wall of said chamberand arranged to form longitudinal circumferentially spaced grooves intheexterior wall of said chamber; and-anelement'of the receiver constructedandarrangedto be attached to the exterior Wall of said chamberbycooperative engagement of said element with the saidlongitudinal'circumferentia-lly-spaced exterior grooves thereof.

'7; Ina firearm'the combination including: a receiver-having abreech-bolt chamber; breechbolt guide-means on the inner-Wall of saidchamber comprising longitudinal circumferentiallyspaced ribs struckinwardly from the exterior wall ofsaid chamber and arranged to formlongitudinal circumferentially spaced grooves in the ex= teriorwall ofsaid chamber; a'triggerplate; and means to'attach said trigger-plate tosaid receiver comprising elements of said trigger-plate arranged toengage in the said longitudinal circumferentially-spaced grooves in theexterior wall of;

said chamber.

8. In a firearm the combination including: a receiver having abreech-bolt chamber breechbolt guide-means on the inner wall of saidchamber comprising circumferentially-spaced ribs struck inwardly fromthe exterior wall of said chamber and arranged to form longitudinalcircumferentially-spaced grooves in the exterior wall of said chamber; atrigger-plate; means to attach said trigger-plate to said receivercomprising resilient spaced-parallel lips on the upper edges of saidtrigger-plate arranged to snap into the said longitudinalcircumferentially-spaced grooves in the exterior wall of said chamber;and fastening-means to secure said trigger-plate to said receiveragainst longitudinal movement with respect thereto.

9. In a firearm the combination including: a receiver having abreech-bolt chamber; breechbolt guide-means on the inner wall of saidchamber said guide-means comprising circumferentially-spaced ribs struckinwardly from the exterior wall of said chamber and arranged to formlongitudinal circumferentially-spaced grooves in the exterior wall ofsaid chamber; a breech-bolt supported on said circumferentially-spacedribs for longitudinal reciprocable movement in said chamber; and atrigger-plate constructed and arranged to be attached to the exteriorwall of said chamber by cooperative engagement with the saidlongitudinal circumferentially-spaced grooves thereof.

10. In a firearm the combination including: a receiver having abreech-bolt chamber; breechbolt guide-means on the inner wall of saidchamher said guide-means comprising circumferentially-spaced ribs struckinwardly from the exterior wall of saidchamber and arranged to formlongitudinal circumferentially-spaced grooves in the exterior wall ofsaid chamber; a breech-bolt supported on said circumferentially-spacedribs for longitudinal reciprocable movement in said chamber; atrigger-plate; and means to attach said trigger-plate to said receivercomprising resilient spaced-parallel lips on the upper edges of saidtrigger-plate arranged to snap into the said longitudinalcircumferentially-spaced grooves in the exterior wall of said chamber.

'11. In a firearm the combination including: a receiver having abreech-bolt chamber; breechbolt guide-means on the inner wall of saidchamber said guide-means comprising circumferentially-spaced ribs struckinwardly from the exterior wall of said chamber and arranged to formlongitudinal circumferentially-spaced grooves in the exterior wall ofsaid chamber; a breech-bolt supported on said circumferentially-spacedribs for longitudinal reciprocable movement in said chamber; atrigger-plate; means to attach said trigger-plate to said receivercomprising resilient spaced-parallel lips on the upper edges of saidtrigger-plate arranged to snap into the said longitudinalcircumferentially-spaced grooves in the exterior wall of said chamber;and fasteningmeans to secure said trigger-plate to said receiver againstlongitudinal movement with respect thereto. I

12. In a firearm the combination including: a receiver; a bushing in theforward end of said receiver, said bushing being arranged to form aforward breech-boltchamber of reduced diameter and the portion of saidreceiver rearwardly of said bushing constituting; a rearward breechboltchamber of relatively-large diameter; breech-bolt guide-means on theinner wall of said rearward chamber comprising circumferentiallyspacedparallel ribs extending longitudinally thereof; abutments at theforwardends of said ribs for engagement by the rear end of said bushing; and abreech-bolt adapted to be mounted in said forward and rearward chambersfor reciprocable movement therein, said breechbolt having a reducedsubstantially-cylindrical forward end arranged to be slidably supportedon'the inside wall of the forward chamber of said receiver and anenlarged substantially-cylindrical rear end arranged to be slidablysupported only by the longitudinally-extending ribs of the rearwardchamber of said receiver.

THOMAS R. ROBINS-ON, JR.

REFERENCES CITED.

The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,291,689 Sheppard Jan. 14, 19192,049,776 Hyde Aug. 4, 1936 2,403,306 Sampson et al July 2, 19462,425,684 Patchett Aug. 12, 1947 2,478,774 Meinel Aug. 9, 1949 2,481,910DArdenne Sept. 13, 1949 FOREIGN PATENTS Number Country 'Date GreatBritain Aug. 12,1946

